Quartz oscillator plate



2;; H948. c. FRONDEL 2,449,844

I QUARTZ OSCILLATOR PLATES Filed Dec. 15, 1944 INVENTOR CL! FFORD FRON DEL ATTORNEYS lating frequency. In a plate Patented Sept. '21, 1948 Clifford Fr ondel. Flushing,

N. Y., anignor to Reeves-Ely Laboratories, Inc., New York. N. Y.. acorporation of New York Application December 15, 1944, Serial No. 588,330

18. Claims.

This invention relates to quartz oscillator plates and has for its object certain improvements in the method of-manufacturlng oscillator plates made of quartz or equivalent material.

In the manufacture of so-called BT quartz oscillator plates, for example, automatic or semiautomatic machines are generally employed in the initial and intermediate states. The final finishing of the plates is, however. still largely a hand operation, the work being done by highly skilled operatives, usually called finishers. In finishing the plates, physical dimensions of the order of sub-millionths of an inch are involved. The finisher is usually provided with a frequency-checking device, a fiat glass plate, fine abrasive, an etching solution, water, a brush, cleaning solutions, lint-free towels. a micrometer, an optical flat. a small square. etc.

The finisher receives the plates. sometimes called blanks, as they come frommechanicai lapping machines, the plates having been cut to substantially proper length and width and usually brought close to, but less than. .the desired oscildesired to have a final frequency of, say, 8000.000 kc., the machine lapping or other pre-hand-finishing treatment is stopped when the plate is from roughly a few hundred cycles up to ten or more'kilocycles under the final desired frequency. A preliminary frequency check is then made by comparing the frequency of the plate with that of a standard plate having a known frequency. This gives the finisher a general idea how much hand lapping the plate should be given. To reduce the plate to its proper thickness, and hence to increase its fre- 2 dip or etching process, the plates as obtained at the completion of the machine lapping are brought up to the desired frequency by dipping them for the required length of time into a solvent for quartz. This solvent, which may be. for example, hydrofluoric acid, removes quartz from the surface of the plate and thus acts to reduce the thickness of the plate to the desired value. This process, as with hand lapping, requires an intermittent, successive. series of treatments and measurements, especiallyin the final stages. to ensure that the desired frequency is exactly attained. The rate of etching of different plates.

of the same initial frequency is not identical, due to variations in the cleanliness of the surface, the roughness of the surface, and other factors. so that a uniform. timed, procedure for all plates can not be set out. In still another method of finishing plates to the desired frequency, the plates are tumbled with an amount of coarse abrasive in a container until the frequency approaches that desired. The plates are then removed, cleaned, and are adjusted to the desired frequency either by etching or hand lapping.

Alternate hand lapping, cleaning and testing are required until the plate reaches the desired .frequency. The activity of the plate is deterquency, the finisher grinds .the plate in a mixture of the abrasive and water on the fiat glass plate, keeping the faces of the plate as fiat and parallel as possible. The plate is next thoroughly cleaned and dried, after which its frequency is again tested. This is done by inserting the carefully cleaned plate in a holder. plugging the holder into an oscillator circuit and noting whether or not the plate has reached the desired oscillating frequency. The lapping of the major plane surfaces of the plates usually is accompanied by a lapping or beveling of the edges of the plates; this operation, by removing roughness and other imperfections from the edges and by altering the edge dimensions, gives the desired degree of activity. socalled, to the plate. 4

The finishing of a plate to its desired frequency also may .be accomplished in other ways, and a number of techniques other than hand lapping have been and are being developed in the oscillator-plate industry. Thus. in the so-called acidmined by its dimensions. contour, parallelism, absence of flaws, cleanness, etc. These physical characteristics are checked, changed. and rechecked until the desired activity is obtained.

The frequency of the plate changes with changes made to the plate to obtain the desired activity.

so that the finisher must coordinate the numerous variables going into the finishing operation to obtain a combination of conditions that yields a plate of predetermined activity and frequency.

Hand finishing by these methods of the oscillator plates is atedious. slow, delicate and costly operation at best and leaves much to be desired. The human factor is an exceedingly important element in these finishing operations and theresults obtained tend naturally to vary from person to person. depending upon the particular technique employed at the time by each finisher.

As a result of my investigation I have discovered that the frequency and certain other characteristics of piezo-electric bodies may be adjusted or varied without altering the physical dimensions of the body. such as by grinding, etching or plating with a metal or other material. The frequency of oscillation of quartz oscillator plates. for example, may be varied. continuously and this variation may be brought under continuous visual control as by an appropriate meter. This perm ts the frequency to be adiusted exactly to a precietermined value or range merely by following the f equency variation on a meter and stopping the treatment at the desired value or within the desired range. This is not possible in present methods of manufacture of piezo-electric bodies which, as noted above, involve a discontinuous alternating process of grinding or etching, cleaning and testing. The frequency of oscillation of quartz oscillator plates may, for example, be readily adjusted to a desired value with an accuracy up to 1 cycle or greater, depending primarily on the accuracy of the measuring device employed. This accuracy cannot be accomplished by the conventional method of grinding or etching because the amount of grinding or etching on which the change of. frequency and accuracy depends cannot be accurately controlled or measured, and

the change in frequency itself cannot be observed continuously.

The frequency of a piezo-electric' body that has been put into a relatively stable state by means of baking, sulfuric acid washing or other treatment, such as'for the purpose of eliminating or reducing spontaneous variation with time in the frequency or activity of the piezo-electric body, can be adjusted without destroying the stability of the piezo-electric body. This is not possible by present methods of manufacture. For example, if a number of quartz oscillator plates are brought by grinding or etching to a desired frequency, and

are then baked or otherwise treated, for the purpose of stabilization, it is found that the frequency often changes erratically from the original' value and must then be adjusted by additional grinding or etching. This action then destroys the stability of the oscillator plate and the purpose of the original stabilizing operation is lost. This readjustment can now be accomplished without grinding or etching and without loss of stability.

The frequency of oscillator plates may be adjusted, for example, without wetting them with water or other liquids and in an entirely dry condition. Water is commonly used in the conventional method of finishing to frequency by lapping with an abrasive or by etching, and has been considered to contribute substantially to undeslrable ageing-and other phenomena in the finished "oscillator plate. be obviated.

The initial change in frequency is downwards from the initial value and is brought about by treating the oscillator plates with radiant energy suitable for that purpose. This may be done, for example, in accordance with the inventions disclosed in my co-pending applications Serial Nos. 568,323, 568,324, now Patent Number 2.437,- 912, 568,325, 568,326, now Patent Number 2,437,- 913, 568,327, 568,328, now Patent Number 2,437,- 914, and 568,329, now Patent Number 2,437,915, flied December 15,, 1944; but the downward change is reversed and the frequency restored to its original or intermediate value by suitable treatment in accordance with the present invention. The new technique is especially advantageous in the recovery of oscillator plates that have been overshot by the ordinary methods of hand finishing. Oscillator plates that have increased in frequency over the upper tolerancedue toageing, or aged low activity plates that have gone over the tolerance after cleaning to bring up the activity, may be similarly-readjusted to their original frequency.

In accordance with the invention, quartz oscillator plates that have been treated .to the ac- This difliculty may now.

. 4 tion of a form of radiant energy adapted to de crease their oscillating frequency are subjected ,to the action of ultra-violet light rays in amount sufficient to increase their oscillating characteristics to a predetermined value or range.

The kinds of energy that are effective to decrease the oscillating frequencies of the oscillator plates include radiations of the wave type, such as X-rays and gamma rays; and radiations consisting of material particles, such as cathode rays or electrons, beta particles or fast electrons, alpha particles and deuterons, as more particularly described in said co-pending applications. The change is progressive and continues during irradiation but finally reaches a limiting value.

determined by factors within the quartz, beyond which there is no further change. The rate of change appears to depend primarily on the kind and intensity of the radiation, but in part on vari-' ations in the properties of the quartz from specimen to specimen and on pre-treatment of the quartz. The continuity of the change is of great importance from a manufacturing point of view. The downward direction of the change is also of particular advantage.

The downward change in frequency brought about by the radiations is permanent under ordinary conditions, but can be reversed and the oscillator plate brought back to its original frequency by baking at a suitably elevated temperature or by irradiating the plate with ultra-violet rays. Ultra-violet rays reverse the action of the other types of radiation. The ability to reverse the downward change is a great advantage. In other words, the oscillator plates may be adjusted downwards and upwards in frequency repeatedly by the proper treatment.

The rate at which the downward change in frequency of the oscillator plates can be effected Y and the total amount of change is influenced by the temperature at which the quartz is held during irradiation, and by previously baking the quartz at a suitably elevated temperature.

These and other features of the invention will be better understood by referring to the accompanying drawing, taken in conjunction with the following description, in which:

Fig. 1 is a diagrammatic cross-sectional reprecury l2. An anode is indicated at 9. The tube is surrounded by a protective housing It provided with a plurality of windows H, M. A

quartz oscillator plate I! is shown in front of window H, the plate being held on a sliding holder l8 movable in an upper track l1 and a lower track l8 by means of a handle is. A stack ofplates IE, it", 15", etc., is shown in front of window I4. I

Referring next to Fig. 2, the apparatus shown comprises a similar evacuated uartz tube II with a quartz oscillator plate I! located in front of window ll of easing II. In. this case, however,

the oscillator plate is mounted in a holder 2|.

The casing of the holder around the oscillator plate s s own broken away in part to expose the divlded to indicate cycles ally heated to a temperature sumciently high to vaporize or hell mercury it. so that the tube be- 1 comes filled with mercury vapor. The resultin ultra-violet light rays 18 pass through tube and window it onto oscillator plate iii, as well as through window i4 onto oscillator plates ll. it", etc. The efi'ect of the ultra-violet rays on each oscillator plate is gradually to increase its oscillating characteristics or frequency. The bombardment of the oscillator plate with the ultra-violet rays may be conducted until the oscillating characteristics or frequency of each oscillator plate falls within a predetermined range or value. In the case of thestack of plates II, II", Wt", the plate nearest window it receives the greatest effect from the radiations, although the next succeeding plates are affected less and less progressively by the radiations. Plate I! may be removed from window it by pulling slide it by means of handle it. a

In using apparatus such as that disclosed in Fig. 2, the desired frequency range or value may be noted visually on frequency meter-ii. When needle 24 is deflected until it points at the desired frequency indicated by scale 25, the oscillator plate is taken out of the path of ultra-violet rays or the source of rays is shut oif.

The change in frequency caused by the ultraviolet rays is upwardly. Oscillator plates irradiated as described in my co-pending applications.

in order to increase their frequency, may be reverted in frequency to their initial or intermediate value when exposed to ultra-violetrays in the manner indicated. The change is accelerated by beating the quartz oscillator plates to loll-150 C.

during irradiation with the ultra-violet rays.

The use of ultra-violet rays offers an important advantage. If for some reason the frequency of an oscillator plate should be decreased too much by the other types of radiation disclosed, its frequency may be increased to the desired value.

It w ll be clear to those skilled in this art that the invention lends itself to numerou modifications. It is possible, for example, to adjust the plate to a desired frequency at a given temperamaterials, such as Rochelle salts. tourmaline, tar trates. etc.' The invention'is applicable to the treatment of any useful piezo-electric material the frequency and oscillating characteristics of vghich are to be variedunder controlled condit one. A

The actual lowest limit of the complete IP trum, containing suillcient of the ultra-violet, as against the x-rays, to be successful for mypresent purpose are not known. Those waves of angstrom unit length from 1850 to 4000 appear best for my purpose. Fluorite is transparent to wave lengths as low as 1200 ang'stromsand lithium to about 1083. With vacuum spectographs having concave gratings, angstroms have been photographed.

In this'lower range there is of course overlapping of'the ultra-violet rays and X-rays and the ture by irradiating the plate, and bringing it to a frequency, while it is held at that temperature in a suitable heating or cooling contrivance. This is not easily accomplished by the conventional lapping or etching techniques of finishing plates.

The rate of change of frequency of the plate during irradiation and also the total amount of frequency change that can be obtained (saturation value) can be modified by baking the quartz plate at a suitable temperature before it is irradiated. Thus, baking the quartz plate at a suitably elevated temperature has been found to increase both the rate of change and the amount of.

change of frequency over that which would obtain if the plate had not been baked beforehand. While the practice of the invention has been described with respect to piezo-electric material in the form of quartz, it will also be clear to" those skilled in this art that the invention is applicable to the treatment of other piece-electric 4'00 angstroms. The ultra-violet band of wave lengths from 1850 ible are completely successful for my purpose. At some placebetween the limits of 1850 and 400 angstroms the ultra-violet ceases to function for my purpose and no change is effected inthe oscil. lator plates. For my present purpose I include in the term or expression ultra-violet light rays" all such portions of the extreme ultra-violet band as function to bring about a frequency change upwardly in a piezoelectric material. Therefore the extreme low of this band with which I am concerned begins some place between 400 and 1850 angstroms and the included band extends up Y to 4000 angstroms. In addition to the quartz mercury lamp herein disclosed, I have used an iron are and a Hanovia hort ultra-violet lamp" as my sources of ultra-violet radiation.

I claim:

1. In the manufacture of quartz oscillator plates that have been irradiated to decrease their frequency of oscillation, the improvement which comprises treating each oscillator plate with ultra-violet light rays adapted to increase it 'frequencyof oscillation.

2. In" the manufacture of quartz oscillator plates that have been irradiated to decrease their frequency of oscillation, the improvement which comprises treating each oscillator plate with ultra-violet light rays adapted to increase its frequency of oscillation, and terminating the treatment or the plate with said u1tra-violet light says when its frequency of oscillation reaches a predetermined value.

3. In the manufacture of quartz oscillator plates that have been irradiatedto decrease their frequency of oscillation, the improvement which comprises treating each oscillator plate while mounted in a holder connected to a frequency meter with ultra-violet light rays adapted to increase the frequency of oscillation of the plate, and terminating the treatment of the plate with said ultra-violet light rays when its frequency of oscillation reaches a. predetermined value.

14. In the manufacture of quartz oscillator plates that have been irradiated to decrease their frequency of oscillation, the improvement which comprises treating each plate while mounted in a holder connected to a frequency meter to the action of ultra-violet light rays adapted to-pass through the housing of the holder and to increase the frequency of oscillation of the plate, and teroscillation reaches a predetermined value.

5. In the manufacture of quartz oscillator wave lengths as short as 40 to 4000 or'from 1850 to the visasses I J plates that have been irradiated to decrease their frequency of oscillation, the improvement which comprises maintaining each oscillator plate at a predetermined temperature, treating each plate;

at said temperature with ultra-violet light waves adapted to. increase its frequency of oscillation, and terminating the. treatment of each cooled plate with said ultra-violet light waves when its frequency of oscillation reaches a predetermined value.

6. In the manufacture of quartz oscillator plates that have been irradiated to decrease their frequency of oscillation, the improvement which comprises cooling each oscillator plate while mounted in a holder connected with a frequency meter, treating the plate while cooled with ultraviolet light waves adapted to increase the frequency of oscillation of the plate, and terminating the treatment of each cooled plate with said ultra-violet light waves when its frequency of oscillation reaches a predetermined value.

'1. In the manufacture of quartz oscillator plates that have been irradiated to decrease their frequency of oscillation, the improvement which comprises maintaining each oscillator plate at a predetermined temperature while mounted in a holder connected with a frequency meter, treating each plate to the action of ultra-violet light waves adapted to increase the frequency of oscillation of the plate, and terminating the treatment of each plate with said ultra-violet light waves when its frequency of oscillation reaches a predetermined value.

8. In the manufacture of quartz oscillator plates that have been ground to a thickness beyond that required to increase its frequency to a predetermined value and that have then been irradiated to decrease their frequency of oscillation, the improvement which comprises treating each plate with ultra-violet light waves adapted to'increaseits frequency of oscillation.

9. 'In the manufacture of quartz oscillator plates that have been ground to a thickness beyond that required to increase its frequency to a predetermined, value and that have then been irradiated to decrease their frequency of oscillation, the improvement which comprises treating each plate with ultra-violet light wave adapted to increase its frequency of oscillation, and terminating the treatment of each ground plate with said ultra-violet light waves when its frequency of oscillation reaches a predetermined value.

10. In the manufacture of quartz oscillator plates that have been ground to a thickness beyond that required to increase its frequency to a predetermined value and that have then been irradiated to decrease their frequency of oscillation, the improvement which comprises maintaim ing .the plate at a predetermined temperature, treating the ground plate while at said temperature with ultra-violet light waves adapted to increase its frequency of oscillation, and terminating the treatment of each ground plate with said ultra-violet light waves when its frequency of oscillation reaches a predetermined value.

11. In the manufacture of quartz oscillator plates that have been etched to a thickness beyond that required to increase its frequency to a predetermined value and that have been irradiated to decrease their frequency of oscillation,

= than desired, the improvement which comprisesviolet light waves when its frequency of oscillation reaches a predetermined value.

12. In the manufacture of quartz oscillatorplates that have been etched to a thickness beyond that required to increase its frequency to a predetermined value and that have been irradiated to decrease their frequency of oscillation, the improvement which comprises maintaining each plate at a predetermined temperature, treating each plate at said temperature with ultra-violet light waves adapted to increase its frequency plates that have been stabilized by baking. acid washing or other treatment, that have been irradiated to decrease their frequency of oscillation and that have a frequency of oscillation lower treating each oscillator plate with ultra-violet light waves adapted to increase its frequency of oscillation, and terminating the treatment of each plate with said ultra-violet light waves when its frequency of oscillation reaches a predetermined value.

14. In the manufacture of quartz oscillator plates that have been irradiated to decrease their frequency of oscillation, the improvement which comprises heating each plate to an elevated temerature to sensitize it to frequency change. treatin each sensitized plate to the action of ultra-violet light rays adapted to increase its frequency of oscillation, and terminating the treatment of each plate with said ultra-violet light rays when its frequency of oscillation reaches a predetermined value.

15. In the manufacture of quartz oscillator plates that have been irradiated to decrease their frequency of oscillation, the improvement which comprises heating each plate to an elevated temperature to sensitize it to frequency change, treating each sensitized plate while mounted in a holder connected to a frequency meter to the action of ultra-violet light rays adapted to increase its frequency of oscillation, and terminating the treatment of each plate with said ultraviolet light rays when its frequency of oscillation reaches a predetermined value.

16. In the manufacture of quartz oscillator,

. plates that have been irradiated to decrease their frequency of oscillation, the improvement which comprises treating such oscillator plates with ultra-violet light rays in the range from 1850 angstroms to 4000 angstroms to increase its frequency of oscillation. 17.'In the manufacture of quartz oscillator plates that have been irradiated to decrease their frequency of oscillation, the improvement which comprises maintaining each oscillator plate at a predetermined temperature, treating each plate the improvement which comprises treating each ing the treatment of each plate with said ultraat said temperature with ultra-violet light rays in the range from 1850 angstroms to 4000 angstroms to increase its frequency of oscillation, and terminating the treatment of each cooled plate with said ultra-violet light rays when its frequency of oscillation reaches a predetermined value.

18. The method of increasing the frequency of oscillation of a piezoelectric oscillator comprising treating such oscillator with ultra-violet light rays in the range from 1850 angstroms to 4000 angstroms.

crm'oan momma. 

